The present invention relates generally to electric field delivery to a prostate tissue of a patient. More particularly, the present invention provides transurethral systems and methods for delivering electrical energy and controlled, mild heating to a prostate tissue of a patient for destruction of cancerous and/or hyperplastic tissue.
The prostate gland is a walnut-sized gland located in the pelvic area, just below the outlet of the bladder and in front of the rectum. It encircles the upper part of the urethra, which is the tube that empties urine from the bladder. The prostate is an important part of the male reproductive system, requiring male hormones like testosterone to function properly, and helps to regulate bladder control and normal sexual functioning. The main function of the prostate gland is to store and produce seminal fluid, a milky liquid that provides nourishment to sperm, and increases sperm survival and mobility.
Cancer of the prostate is characterized by the formation of malignant (cancerous) cells in the prostate. Prostate cancer is the leading cancer related cause of death in men in the United States. There are currently over 2 million men in the United States with prostate cancer, and it is expected that there will be approximately 190,000 new cases of prostate cancer diagnosed, with 28,000 men dying from the disease in 2008.
In addition to risks of morbidity due to prostate cancer, most men over 60 years old experience partial or complete urinary obstruction due to enlargement of the prostate. This condition can originate from prostate cancer, or more typically, from benign prostatic hyperplasia (BPH), which is characterized by an increase in prostate size and tissue mass near the urethra.
Common active treatment options include surgery and radiation. Surgery often includes the complete surgical removal of the prostate gland (“Radical Prostatectomy”), and in certain instances the regional lymph nodes, in order to remove the diseased tissue from the body. In some instances, a nerve sparing prostatectomy is attempted in an effort to maintain erectile function in the patient after treatment. Side effects associated with radical prostatectomy can include pain, inflammation, infection, incontinence, shorter penis and impotence.
Radiation therapy is another treatment option for prostate cancer and is characterized by the application of ionizing radiation to the diseased area of the prostate. Ionizing radiation has the effect of damaging a cells DNA and limiting its ability to reproduce. For Prostate Cancer treatment, two methods of radiation therapy include External Beam Radiation Therapy (EBRT) and internal radiation, commonly known as Brachytherapy. EBRT involves the use of high-powered X-rays delivered from outside the body. The procedure is painless and only takes a few minutes per treatment session, but needs to be done extended periods of five days a week, for about seven or eight weeks. During EBRT, the rays pass through and can damage other tissue on the way to the tumor, causing side effects such as short-term bowel or bladder problems, and long-term erectile dysfunction. Radiation therapy can also temporarily decrease energy levels and cause loss of appetite.
Brachytherapy involves the injection of tiny radioactive isotope containing ‘seeds’ into the prostate. Once positioned in the tissue, the radiation from the seeds extends a few millimeters to deliver a higher radiation dose in a smaller area, causing non-specific damage to the surrounding tissue. The seeds are left in place permanently, and usually lose their radioactivity within a year. Internal radiation also causes side effects such as short-term bowel or bladder problems, and long-term erectile dysfunction. Internal radiation therapy can also temporarily decrease energy levels and cause loss of appetite. It is also common for the implanted seeds to migrate from the prostate into the bladder and then be expelled through the urethra during urination. Most significant, however, is the change in the texture of the prostate tissue over time, making the subsequent removal of the gland, as described above, complicated and difficult as a secondary treatment.
Given the significant side-effects with existing treatments such as radical prostatectomy and radiation therapy, less invasive and less traumatic systems and procedures have been of great interest. One such more minimally invasive system developed in recent years includes so called “Trans-urethral Needle Ablation” or TUNA, which involves passing a radio-frequency (RF) device such as a catheter probe or scope into the urethra for delivery of high frequency energy to the tissue. The RF instruments include electrode tips that are pushed out from the side of the instrument body along off-axis paths to pierce the urethral wall and pass into the prostatic tissue outside of the urethra. High-frequency energy is then delivered to cause high-temperature ionic agitation and frictional heating to tissues surrounding the electrodes. The high-temperature induced in the tissue includes induction of extremely high temperatures, often up 100 degrees C., and is generally is non-specific to cancerous tissue, destroying both healthy and non-healthy tissue.
Another technique developed in recent years for treating BPH is Trans-urethral Microwave Thermo Therapy (or “TUMT”). This technique involves use of a device having a microwave probe or antenna located near its distal end and connected to an external generator of microwave power outside the patient's body. The microwave probe is inserted into the urethra to the point of the prostate for energy delivery and microwave electromagnetic heating. Since the microwave probe delivers substantial heating that can cause unwanted damage to healthy tissues or to the urethra, devices typically make use of a cooled catheter to reduce heating immediately adjacent to the probe. The objective is to carefully balance cooling of the urethra to prevent damage to it by the heating process, while at the same time delivering high temperature heating (greater than 50 degrees C.) to the prostatic tissue outside of and at a distance from the urethra. In this procedure, the prostatic tissue immediately around the urethra and the urethra itself are deliberately spared from receiving an ablative level of heating by attempting to keep the temperatures for these structures at less than 50 degrees C. Unfortunately, controlling the tissue heating due to the applied microwave energy is difficult and unintended tissue damage can occur. Further, destruction of tissue beyond the cooled region is indiscriminate, and control of the treatment zone is imprecise and limited in the volume of tissue that can be effectively treated.
Accordingly, there is a continuing interest to develop less invasive devices and methods for the treatment of BPH and prostate cancer that is more preferential to destruction of target tissue and more precisely controllable.